The present invention pertains in general to a method and apparatus for splitting flow and in particular to a method and apparatus for splitting the flow of a vapor-liquid mixture.
In oil fields where steam is injected into a formation as part of an enhanced oil recovery (EOR) program, it is important to know the quantity and quality (ratio of steam to water) of steam being injected into each of a plurality of wells. Planning an injection program for each well and evaluating its effectiveness require a knowledge of conditions in each well. Implementing an effective EOR program requires the ability to control the quality and quantity of steam delivered to each well.
Although the quantity of steam applied to each well may be effectively controlled by valves or chokes, it is difficult to obtain a desired quality for each of a plurality of injection wells from a single steam source. When the flow of steam is split, different amounts of liquid water might flow into each of the split branches of the flow.
To predictably split the flow of a liquid-vapor mixture, one approach involves providing an inlet at the top of a vessel having a plurality of outlet pipes projecting upward through the bottom of the vessel to equal heights, as found for example in U.S. Pat. Nos. 3,899,000, 4,140,178 and 4,293,025. A splash baffle between the inlet and outlet pipes prevents substantially all liquid in the flow from falling directly into the outlet pipes. The liquid accumulates in the vessel and enters the outlet pipes by spilling over the lip of the open end of each outlet pipe or through holes bored in the side of each outlet pipe. One drawback to this approach is that it removes virtually all liquid from the flow so that a large vessel is required at a correspondingly large cost. Another drawback is that in order to accommodate the outlet pipes, the vessel may have to be specially made, particularly in the larger sizes, because large enough vessels having the required wall thickness for use with steam are not readily available.
Another approach, exemplified by U.S. Pat. No. 4,396,063, passes the mixture to be split through a motionless mixer in order to homogenize the liquid and vapor phases and then immediately passes the mixture against a blade in a "wye" conduit. This approach has the disadvantages of requiring the use of non-standard equipment and of assuming that liquid that drops out at the wye will be re-entrained in the flow in equal amounts down each branch.
Absent from either approach is the ability to inexpensively and reliably divide a flowing liquid-vapor mixture into streams of substantially equal quality.